JP7230653B2 - Thin film capacitor and multilayer circuit board with embedded thin film capacitor - Google Patents

Description

The present invention relates to a thin film capacitor and its manufacturing method, and more particularly to a thin film capacitor that can be manufactured at low cost, its manufacturing method, and a multilayer circuit board in which the thin film capacitor is embedded.

A thin film capacitor is mainly used as a decoupling capacitor that stabilizes the power supply voltage. For example, Patent Documents 1 and 2 disclose interposer-type thin film capacitors.

JP 2017-130653 A JP 2017-173386 A

However, since the thin film capacitor described in Patent Document 1 has a build-up structure, there is a problem that the manufacturing process is complicated. In addition, the thin film capacitor described in Patent Document 2 is formed on a support substrate made of an insulator such as silicon. There was a problem that the process was complicated.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a thin film capacitor that can be manufactured at low cost, a method for manufacturing the same, and a multilayer circuit board in which the thin film capacitor is embedded.

A thin film capacitor according to the present invention comprises: a capacitive insulating film provided with a plurality of through holes including first and second through holes; a first metal film provided on one surface of the capacitive insulating film; a second metal film provided on the other surface of the film and made of a metal material different from that of the first metal film; A first space is provided, whereby the first metal film is separated into a first region located outside the first space and a second region located inside the first space. The second metal film is provided with a second space surrounding the second through hole in plan view, whereby the second metal film is positioned outside the second space. and a fourth region located inside the second space, the third region of the second metal film passing through the first through hole and the first It is connected to the second region of the first metal film through the first connecting portion provided so as to cut into the metal film, and the fourth region of the second metal film extends through the second through hole. It is characterized in that it is connected to the first region of the first metal film via a second connection portion that is provided so as to penetrate and bite into the first metal film.

According to another aspect of the present invention, there is provided a multilayer circuit board in which the thin film capacitor described above is embedded.

According to the present invention, the first and second metal films are arranged on the front and back sides of the capacitive insulating film without using a support substrate made of an insulator, and the first and second through holes are provided in the capacitive insulating film. Since the two are connected via the , it can be manufactured at a lower cost than a build-up structure or a structure in which a through hole is provided in the support substrate, and the overall thickness can be made thinner. . Moreover, since the first and second connection portions of the second metal film are provided so as to cut into the first metal film, the adhesion between the first metal film and the second metal film is also enhanced. be done.

In the present invention, the capacitive insulating film may be made of a ceramic material. As the ceramic material, it is possible to use, for example, a ceramic material having a perovskite structure.

In the present invention, the first metal film may be made of Ni and the second metal film may be made of Cu. According to this, the capacitive insulating film made of a ceramic material can be fired while the first metal film and the capacitive insulating film are stacked.

In the present invention, the first connection portion and the second connection portion may have different depths of biting into the first metal film. According to this, since the position where the potential difference generated at the dissimilar metal joint surface due to the temperature difference varies in the depth direction, it is possible to alleviate the noise component caused by the potential difference.

In the present invention, an inorganic substance or an organic substance derived from the process of forming the capacitive insulating film is locally present on the other surface of the capacitive insulating film, and one of the first and second connecting portions is covered with the inorganic substance or the organic substance. The other of the first and second connection portions is provided through a portion that is not covered with an inorganic substance or an organic substance, and one of the first and second connection portions is provided through the second The depth of bite into the first metal film may be shallower than the other of the first and second connection portions. The inorganic or organic matter derived from the process of forming the capacitive insulating film is specifically an inorganic or organic matter that inevitably exists as inclusions mixed in from the process. According to this, local electric field concentration is reduced, and leakage current can be reduced.

In the present invention, a barrier metal may be provided at the interface between the first metal film and the second metal film. This makes it possible to prevent migration of the first metal film or the second metal film.

A thin film capacitor according to the present invention further comprises a third metal film laminated on the first metal film and having the same planar shape as the first metal film, wherein the second metal film and the third metal film are made of the same metal. It may be made of material. According to this, it is possible to eliminate the directionality of the front and back.

A method of manufacturing a thin film capacitor according to the present invention includes a first step of forming a capacitive insulating film on the surface of a first metal film, forming first and second through holes in the capacitive insulating film, and forming first and second through holes in the capacitive insulating film. a second step of forming recesses in the first metal film by over-etching the first metal film exposed from the through holes 2; a third step of forming a second metal film made of a metal material different from that of the first metal film inside and in the concave portion of the first metal film; A fourth step of providing a first space surrounding the through-hole of the second metal film and providing a second space surrounding the second through-hole in plan view in the second metal film.

According to the present invention, the first metal film and the second metal film are connected via the first and second through holes provided in the capacitor insulating film, and the first metal film surrounding the first through hole is connected. Since the space is provided in the first metal film and the second space surrounding the second through-hole is provided in the second metal film, it is possible to manufacture an interposer type thin film capacitor through a simple process. Become. Moreover, since the first metal film is over-etched when the first and second through holes are formed in the capacitor insulating film, the second metal film can be made to bite into the first metal film. This also makes it possible to improve the adhesion between the first metal film and the second metal film.

Thus, according to the present invention, it is possible to provide a thin film capacitor that can be manufactured at low cost, a method for manufacturing the same, and a multilayer circuit board in which the thin film capacitor is embedded.

FIG. 1 is a schematic cross-sectional view for explaining the structure of a thin film capacitor 1 according to a first embodiment of the invention. FIG. 2 is a schematic plan view of each layer constituting the thin film capacitor 1, in which (a) is the shape of the second metal film 20, (b) is the capacitive insulating film 40, and (c) is the shape of the first metal film 10. is shown. 3A to 3D are process diagrams for explaining the method of manufacturing the thin film capacitor 1. FIG. 4A to 4D are process diagrams for explaining the method of manufacturing the thin film capacitor 1. FIG. FIG. 5 is a schematic diagram for explaining the reason why the depth of overetching differs depending on the through-hole. FIG. 6 is a schematic diagram for explaining the reason why the step 51 is formed on the bottom surface of the concave portion 50. As shown in FIG. FIG. 7 is a schematic diagram for explaining the reason why the protrusion 52 is formed on the bottom surface of the recess 50. As shown in FIG. FIG. 8 is a schematic cross-sectional view for explaining the structure of a thin film capacitor 2 according to a second embodiment of the invention. FIG. 9 is a schematic cross-sectional view for explaining the structure of a thin film capacitor 3 according to a third embodiment of the invention. FIG. 10 is a schematic cross-sectional view for explaining the structure of a multilayer circuit board 80 in which the thin film capacitor 1 according to the first embodiment is embedded.

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic cross-sectional view for explaining the structure of a thin film capacitor 1 according to a first embodiment of the invention.

As shown in FIG. 1, the thin film capacitor 1 according to the first embodiment includes a capacitive insulating film 40, a first metal film 10 and a second metal film 20 formed on the front and back sides of the capacitive insulating film 40, and a second A third metal film 30 is provided so as to overlap with the first metal film 10 . FIG. 2 is a schematic plan view of each layer constituting the thin film capacitor 1, in which (a) is the shape of the second metal film 20, (b) is the capacitive insulating film 40, and (c) is the shape of the first metal film 10. is shown. Also, FIG. 1 shows a cross section along line AA shown in FIG.

The capacitive insulating film 40 is made of a ceramic material having a perovskite structure such as barium titanate. A first through hole 41 and a second through hole 42 are formed in the capacitive insulating film 40 . The first through holes 41 and the second through holes 42 are alternately arranged in one direction.

The first metal film 10 is made of Ni (nickel), for example, and is formed on one surface of the capacitive insulating film 40 . A first space C1 is provided in the first metal film 10 at a position surrounding the first through hole 41 in plan view. Thereby, the first metal film 10 is separated into a first region 11 positioned outside the first space C1 and a second region 12 positioned inside the first space C1. The first region 11 and the second region 12 are insulated by the first space C1, one of which is used as the positive electrode of the thin film capacitor and the other as the negative electrode of the thin film capacitor. The reason why Ni (nickel), for example, is used as the material of the first metal film 10 is that the first metal film 10 is used as a support for the capacitor insulating film 40 in the step of firing the capacitor insulating film 40, as will be described later. Therefore, it is necessary to withstand high temperatures.

The second metal film 20 is made of Cu (copper), for example, and is formed on the other surface of the capacitor insulating film 40 . A second space C2 is provided in the second metal film 20 at a position surrounding the second through hole 42 in plan view. Thereby, the second metal film 20 is separated into a third region 23 positioned outside the second space C2 and a fourth region 24 positioned inside the second space C2. The third region 23 and the fourth region 24 are insulated by the second space C2, one of which is used as the positive electrode of the thin film capacitor and the other as the negative electrode of the thin film capacitor. The reason why Cu (copper), for example, is used as the material of the second metal film 20 is that it has a low resistance value and is easy to form by electroplating.

The third metal film 30 is made of Cu (copper), for example, and laminated on the first metal film 10 . The third metal film 30 has the same planar shape as the first metal film 10 .

As shown in FIG. 1 , the second metal film 20 is connected to the first metal film 10 through through holes 41 and 42 provided in the capacitor insulating film 40 . More specifically, the third region 23 of the second metal film 20 has a first connecting portion 21 penetrating through the first through hole 41 and the first It is connected to the second region 12 of the metal film 10 . On the other hand, the fourth region 24 of the second metal film 20 has the second connection portion 22 passing through the second through hole 42 , and the second connection portion 22 is interposed between the first metal film 10 and the fourth region 24 . It is connected to the first region 11 .

Thereby, the first region 11 of the first metal film 10 and the fourth region 24 of the second metal film 20 are electrically short-circuited. Similarly, the second region 12 of the first metal film 10 and the third region 23 of the second metal film 20 are electrically shorted. Then, as shown in FIG. 1, the first region 11 of the first metal film 10 and the third region 23 of the second metal film 20 overlap each other with the capacitive insulating film 40 interposed therebetween. Therefore, a capacitance is obtained in this portion. As a result, the first region 11 of the first metal film 10 (the fourth region 24 of the second metal film 20) is one of the positive and negative electrodes, and the second region 12 of the first metal film 10 (the fourth region 24 of the second metal film 20). A thin film capacitor having the third region 23) of the second metal film 20 as the other of the positive electrode and the negative electrode is constructed.

In this embodiment, since both the positive electrode and the negative electrode appear on the front and back sides of the thin film capacitor 1, it can be used as an interposer. Moreover, since the pattern shapes on the front and back are the same except that the positions of the spaces C1 and C2 are shifted by one pitch, it can be used as an interposer having no directivity on the front and back.

Furthermore, in the present embodiment, since the first and second connection portions 21 and 22 that are part of the second metal film 20 are provided so as to bite into the first metal film 10, the first The adhesion between the metal film 10 and the second metal film 20 is also enhanced. As a concrete depth of bite, it is preferable to set it to 2 μm or less. This is because forming recesses exceeding 2 μm increases the load on the process and lowers the productivity.

Although not particularly limited, the depth of penetration of the first and second connecting portions 21 and 22 into the first metal film 10 may be different from each other. Further, the depth of bite into the first metal film 10 may be different for each of the plurality of first connecting portions 21, and each of the plurality of second connecting portions 22 may be The depth of bite into the first metal film 10 may be different from each other.

Here, when heat is applied to the thin film capacitor 1 from a processor or the like, a potential difference is generated between the junction surfaces of the first metal film 10 and the second metal film 20 made of different metals. Such a potential difference may become a noise component of the decoupling capacitor. Since there is variation in the direction, noise components can be mitigated.

Next, a method for manufacturing the thin film capacitor 1 according to this embodiment will be described.

3 and 4 are process diagrams for explaining the method of manufacturing the thin film capacitor 1 according to this embodiment.

First, as shown in FIG. 3A, a capacitive insulating film 40 made of barium titanate or the like is formed on the surface of a first metal film 10 made of Ni or the like and fired. At this time, a high temperature is also applied to the first metal film 10, but by using a high melting point metal such as Ni as the material of the first metal film 10, it is possible to withstand the firing temperature.

Next, as shown in FIG. 3B, the capacitive insulating film 40 is etched to form first and second through holes 41 and 42 . At this time, recesses 50 are formed in the first metal film 10 by overetching even after the first and second through holes 41 and 42 are formed. The depth of the recess 50 depends on whether the through-holes 41 and 42 are formed in a portion covered with an insulating material or organic material derived from the capacitive insulating film forming process, or is not covered with an insulating material or organic material derived from the capacitive insulating film forming process. It differs depending on whether through holes 41 and 42 are formed in the part.

That is, as shown in FIG. 5A, when etching is performed on a portion of the capacitor insulating film 40 that is not covered with an insulating material or an organic material derived from the process of forming the capacitor insulating film, the first metal film 10 The depth Z1 of the recess 50 formed by the over-etching is as designed, but as shown in FIG. When etching is performed on the exposed portion, the depth Z2 of the recess 50 formed by overetching of the first metal film 10 becomes shallower than the designed value (Z1>Z2). This is because the progress of etching is slowed down by the presence of the insulating material or organic material 60 derived from the process of forming the capacitor insulating film. In addition, since the thickness of the insulating material or organic material 60 derived from the process of forming the capacitive insulating film also varies, the depth of the concave portion 50 varies.

6(a), when the region 43 overlapping the edge portion of the insulator or organic substance 60 derived from the capacitor insulating film forming process is etched, as shown in FIG. 6(b), , a step 51 is formed on the bottom surface of the recess 50 . Furthermore, as shown in FIG. 7(a), when the plane size of the insulator or organic matter 60 derived from the process of forming the capacitive insulating film is small and the etching is performed for the region 44 including the entirety, As shown in b), a protrusion 52 is formed on the bottom surface of the recess 50 . As described above, depending on the relationship between the position of the insulating material or organic material 60 derived from the capacitor insulating film formation process and the etching area, a step 51 or a protrusion 52 may be formed on the bottom surface of the recess 50 .

Next, as shown in FIG. 3C, a seed layer 20a is formed on the entire surface by sputtering or the like. As a result, the seed layer 20 a is formed not only on the surface of the capacitor insulating film 40 , but also on the inner walls of the through holes 41 and 42 and the inner walls of the recess 50 . The seed layer 20a preferably uses a laminated film of Ni and Cu.

Next, as shown in FIG. 4A, the second metal film 20 made of Cu is formed by electroplating using the seed layer 20a as a power supply. As a result, the second metal film 20 is formed on the surface of the capacitor insulating film 40 , inside the first and second through holes 41 and 42 , and in the recess 50 of the first metal film 10 . After that, as shown in FIG. 4B, the second metal film 20 is separated into the third region 23 and the fourth region 24 by forming the second space C2.

Then, as shown in FIG. 4C, after forming a third metal film 30 made of Cu on the back surface of the first metal film 10, the first and third metal films 10 and 30 are coated with the first film. By forming the space C1 to separate the first region 11 and the second region 12, the thin film capacitor 1 shown in FIG. 1 is completed.

As described above, the thin film capacitor 1 according to the present embodiment has the first metal film 10 and the second metal film 20 arranged on the front and back sides of the capacitive insulating film 40 without using an insulating substrate or the like. Since both are connected through the through holes 41 and 42 formed in 40, it is possible to obtain a thin structure suitable for the interposer. Moreover, since the first and second connection portions 21 and 22, which are part of the second metal film 20, are provided so as to bite into the first metal film 10, the first metal film 10 and the second The adhesion of the metal film 20 of 2 is also ensured.

FIG. 8 is a schematic cross-sectional view for explaining the structure of a thin film capacitor 2 according to a second embodiment of the invention.

As shown in FIG. 8, the thin film capacitor 2 according to the second embodiment differs from the thin film capacitor 1 according to the first embodiment in that a barrier metal 70 is provided under the second metal film 20. ing. Since other configurations are the same as those of the thin film capacitor 1 according to the first embodiment, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted.

The barrier metal 70 is provided to prevent migration from the second metal film 20 to the first metal film 10, and is made of a material having a higher melting point than the second metal film 20, such as tungsten. can be used.

FIG. 9 is a schematic cross-sectional view for explaining the structure of a thin film capacitor 3 according to a third embodiment of the invention.

As shown in FIG. 9, the thin film capacitor 3 according to the third embodiment differs from the thin film capacitor 1 according to the first embodiment in that the third metal film 30 is omitted. Since other configurations are the same as those of the thin film capacitor 1 according to the first embodiment, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted.

As illustrated in this embodiment, it is not essential to provide the third metal film 30 in the present invention, and the first metal film 10 made of Ni or the like may be used as it is as an external terminal.

FIG. 10 is a schematic cross-sectional view for explaining the structure of a multilayer circuit board 80 in which the thin film capacitor 1 according to the first embodiment is embedded.

In the example shown in FIG. 10, a multilayer circuit board 80 has wiring layers L1 to L8, and an interlayer insulating film 81 is provided between adjacent wiring layers. Different wiring layers are connected to each other through via conductors 82 . A plurality of IC chips 91 to 93 are mounted on the uppermost wiring layer L8. The thin-film capacitor 1 is embedded in the multi-layer circuit board 80 having such a configuration, the via conductor 82a to which the power supply potential is applied, for example, is connected to the third region 23 of the second metal film 20, and the via conductor to which the ground potential is applied. By connecting 82b to the fourth region 24 of the second metal film 20, the thin film capacitor 1 functions as a decoupling capacitor.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. Needless to say, it is included within the scope.

1 to 3 thin film capacitor 10 first metal film 11 first region 12 second region 20 second metal film 20a seed layer 21 first connecting portion 22 second connecting portion 23 third region 24 fourth region 30 third metal film 40 capacitive insulating film 41 first through-hole 42 second through-holes 43, 44 etching region 50 concave portion 51 step 52 protrusion 60 insulator or organic substance derived from capacitive insulating film forming process 70 barrier metal 80 multilayer circuit board 81 interlayer insulating films 82, 82a, 82b via conductors 91 to 93 IC chip C1 first space C2 second space

Claims (8)

a capacitive insulating film provided with a plurality of through holes including first and second through holes;
a first metal film provided on one surface of the capacitive insulating film;
a second metal film provided on the other surface of the capacitive insulating film and made of a metal material different from that of the first metal film;
a third metal film laminated on the first metal film and having the same planar shape as the first metal film;
the second metal film and the third metal film are made of the same metal material,
The first metal film is provided with a first space surrounding the first through hole in plan view, whereby the first metal film is outside the first space. separated into a first region located in and a second region located inside the first space,
The second metal film is provided with a second space surrounding the second through hole in plan view, whereby the second metal film is outside the second space. separated into a third region located in and a fourth region located inside the second space,
The third region of the second metal film passes through the first through hole and is connected to the first metal film via a first connecting portion provided to bite into the first metal film. connected to the second region of one metal film;
The fourth region of the second metal film is connected to the second metal film via a second connection portion that penetrates the second through hole and bites into the first metal film. 1. A thin film capacitor connected to said first region of a metal film. 2. A thin film capacitor according to claim 1, wherein said capacitive insulating film is made of a dielectric material having a perovskite structure. 3. The thin film capacitor according to claim 1, wherein said first metal film is made of Ni and said second metal film is made of Cu. 4. The thin film capacitor according to claim 1, wherein the first connecting portion and the second connecting portion have different depths of biting into the first metal film. An inorganic substance or an organic substance derived from the process of forming the capacitive insulating film is locally present on the other surface of the capacitive insulating film,
one of the first and second connecting portions is provided through the portion covered with the inorganic or organic substance,
The other of the first and second connection portions is provided through a portion not covered with the inorganic or organic substance,
5. The one of the first and second connection portions is shallower than the other of the first and second connection portions intruding into the first metal film. The thin film capacitor according to . 6. The thin film capacitor according to claim 1, wherein a barrier metal is provided at an interface between said first metal film and said second metal film. a capacitive insulating film provided with a plurality of through holes including first and second through holes;
a first metal film provided on one surface of the capacitive insulating film;
a second metal film provided on the other surface of the capacitive insulating film and made of a different metal material from the first metal film,
A barrier metal is provided at an interface between the first metal film and the second metal film,
The first metal film is provided with a first space surrounding the first through hole in plan view, whereby the first metal film is outside the first space. separated into a first region located in and a second region located inside the first space,
The second metal film is provided with a second space surrounding the second through hole in plan view, whereby the second metal film is outside the second space. separated into a third region located in and a fourth region located inside the second space,
The third region of the second metal film passes through the first through hole and is connected to the first metal film via a first connecting portion provided to bite into the first metal film. connected to the second region of one metal film;
The fourth region of the second metal film is connected to the second metal film via a second connection portion that penetrates the second through hole and bites into the first metal film. 1. A thin film capacitor connected to said first region of a metal film. A multilayer circuit board in which the thin film capacitor according to any one of claims 1 to 7 is embedded.

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